The past and the present are combined in the Missouri quarter design.
Lewis and Clark's Corps of Discovery set out to navigate the Missouri River in 1804, and the Gateway Arch was built in 1965.

Putting the two features together tells what an important part Missouri played in Americans moving west.
For a number of years, Missouri was the state farthest west in the United States, so it was a good place for settlers to form wagon trains and begin their journeys.
Even though Missouri was not yet a state in 1804 (it was still part of the Louisiana Territory), St. Charles was a city, and the Corps of Discovery used it as the starting point for their history-making exploration.